A Marine Protected Area (MPA) is often defined as any area of intertidal or subtidal terrain, together with its overlaying water and associated fauna, flora, historical and cultural features, which has been reserved by law or other effective means to protect part or all of the enclosed environment (Kelleher and Kenchington, 1992).
However, other definitions of MPAs exist.

The type of Marine Protected Area (MPA) depends on the legislative measure in place to provide protection to the marine species and habitats that occur in them.
Sites may be protected as part of European or national legislation. MPAs designated as part of the European Natura 2000 network and referred to collectively as European Marine Sites (EMS) are Special Areas of Conservation (SACs) and Special Protection Areas (SPAs). SACs, in addition to SPAs and Marine Nature Reserves (MNRs) are protected by statutory obligations. The UK also has voluntary MPAs such as Voluntary Marine Conservation Areas (VMCAs) and Voluntary Marine Nature Reserves (VMNRs).
In addition, there are areas closed to fishing using bottom trawling and static gear to protect deep-water corals, such as the North East Atlantic Fisheries Commission (NEAFC) closed areas at Hatton and Rockall Banks.

Many human activities are damaging or cause disturbance to marine habitats, species and ecosystem processes.
This damage can affect the supply of ecosystem goods and services that marine biodiversity provides us with. These include regulating the earth's climate, cycling nutrients, recreation, and providing raw materials such as oil and gas, aggregates and food. Therefore it is very important to protect and conserve the marine environment and thereby safeguard our natural heritage for future generations to enjoy. Marine Protected Areas (MPAs) provide a practical and significant contribution to the recovery and conservation of marine species and habitats. The best available scientific information tells us that we must establish MPA networks across 20 to 30 percent of our seas and oceans. Networks must be representative in terms of different ecosystems, habitats and communities and may have different uses and levels of protection within them, but all should include reserves or no take zones (NTZs). When MPAs are designed as a network and supported by wider environment management measures, they promote the recovery and conservation of ecosystem structure and function.

2 no take zones : Lamlash Bay on the east coast of Arran, and around Lundy in Devon.

1 Marine Conservation Zone (MCZ) around Lundy in Devon.

In England there are also 28 SSSIs that are not part of SACs but have marine features

How much of the UK Seas are protected?

In total , the area coverage of all UK Marine Protected Areas (Including designated and candidate SACs, SPAs, MCZs, NTZs and MNRs) is roughly 4.1 million hectares, or around 4.0 % of UK waters.

What is a No Take Zone?

A No Take Zone (NTZ) is a Marine Protected Area (MPA) permanently set aside from direct human disturbance , where all methods of fishing and extraction of natural materials, dumping, dredging or construction activities are prohibited , from which the removal of any resources, living or dead is prohibited. NTZs can be used alongside conventional fisheries and wildlife conservation management measures in order to protect marine wildlife and heritage and safeguard or improve local fish stocks for future generations to enjoy. NTZs may be in isolation, surrounded by normal fishing grounds, or form part of a larger marine reserve, managed for nature conservation, with managed buffer zones around the NTZ.

The main tool for marine conservation outlined in the Act is the creation of Marine Conservation Zones; a network of Marine Protected Areas aimed to halt the decline in biodiversity by including the full range of UK habitats and species and conserving areas where there are rare and threatened species and habitats to ensure that the marine environment is healthy and able to deliver the many goods and services we rely on.

The Act will be applied in different ways for different areas of the seas around the UK, and Defra have released Maps to explain how (click here)

What is a Marine Conservation Zone (MCZ)?

Marine Conservation Zones are a new designation tool included in the Marine and Coastal Access Act that can be designated to conserve and/or aid the recovery of: the range of marine biodiversity in our waters; rare or threatened habitats and species; and features of geological or geomorphological interest. MCZs will apply to UK offshore waters, and English and Welsh territorial waters.

The Act provides the tools needed to designate and protect a network of sites - Marine Conservation Zones (MCZs) - which will provide protected areas covering habitats and species which exist in our seas. MCZs will be both large enough, and close enough together, to support functioning communities of marine wildlife. MCZs will be used to protect areas that are important to conserve the diversity of rare, threatened and representative habitats and species [Ref: Marine and Coastal Access Act Policy Statement].